1. Field of the Invention
This invention relates to the field of communications systems and, in particular, to transmission of message signals in a communications system.
2. Description of Related Art
It is well known that it is desirable to reduce the receive and decode delay of frames of data transmitted from a transmitter to a receiver in a communications system. For example, it is desirable to reduce frame delay when information is transmitted through a broadcast channel in a cellular system. Among other things, a reduced delay will allow mobile units to access the cellular system in a faster manner.
Some delay can be tolerated when voice telephones access a cellular system in order to initiate a call. In the case of cell handoff, if the amount of delay is relatively small then it is unnoticeable to the user. However, if the delay becomes too large, it can result in a call being dropped by the system.
High data rate terminals are an example where receive and decode delay is critical. These terminals frequently go on and off line and the access delay can slow applications and result in congestion at the data source. Additionally, in soft handoff even a short delay can produce significant congestion or loss of data.
It is known in the prior art to reduce frame size in order to reduce this delay problem. However, this solution reduces the coding gain or the amount of data that can be transmitted as well as interleaving gain. In order to partially compensate for the loss incurred using this method, the power of the channel can be increased or other methods such as the R-RAKE technique can be used. Additionally increasing the power of the channel will decrease the total capacity of the system. Moreover, the R-RAKE compensation technique requires two or more frames in a row to be the same, and the receiver must be able to know or detect this condition. It can be difficult or troublesome for a system to make this determination.